This invention concerns an advanced rotary positive displacement engine having high power to mass ratio and low production cost. Engine as used in this patent document is taken to be a device that converts one form of energy into another. An exemplary pump and an exemplary external combustion engine are disclosed embodying the novel design principles of the invention.
In the case of prior art combustion engines, the reciprocating piston type is most widely used for its low cost of production and efficient sealing, while the turbine has shown that an external combustion engine may offer greater power partially from high speed. Rotary engines such as the Wankel engine have shown higher power to weight ratios than reciprocating engines but at the expense of increased fuel consumption. The present invention is a rotary device that offers many of the advantages of these prior art devices without many of their shortcomings.
In the case of pumps, there are many general types of pump design known, such as positive displacement, centrifugal and impeller. Pumps of the positive displacement type are typically reciprocating or rotary.
Many previous rotary combustion engine designs have been of the single plane type in which rotary motion occurs about axes that are parallel to each other.
The present invention is of the rotary positive displacement type, but is in a class by itself. This rotary positive displacement device is believed to be the first rotary engine in which the axes of the moving parts are offset from each other and the moving parts rotate at a constant velocity relative to each other when they are rotating at a constant velocity relative to the casing. The engine is formed by a pair of facing rotors that are axially offset from another and whose faces define chambers that change volume with rotation of the rotors.
An engine of this type defines a new class of engines, and includes a minimum number of moving parts, namely as few as two in total.
In one aspect of the invention, a pump includes a pair of rotors, both housed on and preferably within the same housing. The housing has an interior cavity having a center. Each rotor is mounted on an axis that passes through the center of the cavity, the respective axes of the rotors being at an angle to each other, with the center of each rotor being at the center of the cavity. The rotors interlock with each other to define chambers. Vanes defined by a contact face on one side of the vane and a side face on the other side of the vane protrude from the rotors. Each contact face of one rotor is defined by the rotation of a conical section of material at the tip of a vane on the other rotor, so that there is constant linear contact between opposing vanes on the two rotors as they rotate. The side faces are preferably concave and extend from an inner end of one contact face to the outer end of an adjacent contact face, equivalent to the tip of a vane. The side faces and contact faces define walls of chambers that change volume as the rotors rotate. Ports for intake and exhaust are preferably configured to have shapes complementary to the intersecting vanes of the rotors.
In a further aspect of the invention, an external combustion engine is provided in which one power rotor having an axis A rotates within a passive rotor having axis B offset to axis A. The rotors share a common center, and the axes intersect at the common center. Pistons extend radially from the power rotor into cylinders formed in the passive rotor. The pistons contact the walls of the cylinder on 180.degree. of rotation (top to bottom) and do not contact on the next 180.degree. of rotation (bottom to top). As the rotors rotate, the pistons move axially within the cylinders changing the volume of the chambers inside the cylinders.
These and other aspects of the invention will be described in more detail in what follows and claimed in the claims appearing at the end of this patent document.